The present invention relates to a method of and to an apparatus for transporting rod-shaped articles of the tobacco processing industry, especially for transporting sections of filter rods. More particularly, the invention relates to a method of and to an apparatus for pneumatically transporting rod-shaped articles of the tobacco processing industry axially between an article discharging station (known as a sender) and an article receiving station (known as a receiver) by way of a pneumatic conveyor wherein the articles are advanced by a compressed gaseous carrier medium, normally air.
It is well known to transport rod-shaped articles of the tobacco processing industry from an article discharging station (such station can receive articles from one or more magazines or one or more makers) to one or more remote receiving stations (e.g., to the magazine or magazines of one or more processing machines) by way of a pneumatic conveyor pipe wherein the articles are propelled by compressed air. It is also known to provide in the conveyor pipe means for ensuring that the articles are singularized prior to arrival at the receiving station, namely that successive articles are separated from each other by gaps of prescribed width. This is desirable and necessary because, upon arrival at the receiving station, the articles are frequently caused to switch from axial movement to a movement at right angles to their axes. In the absence of gaps between successive articles, the next-following articles could interfere with sidewise transport of the immediately preceding articles and any frictional and/or other contact between such articles (e.g., between the front end face of the trailing article and the rear end face of the preceding article) could result in deformation, other damage or total destruction.
In modern high-speed production lines for the making of filter cigarettes or the like, the frequency at which successive rod-shaped articles (coming, for example, from a filter rod making machine or from a magazine for filter rod sections) are propelled into the inlet of a pneumatic conveyor pipe is so high that the kinetic energy of pneumatically propelled articles is quite pronounced. Therefore, it is even more important to prevent undesirable contact between successive articles at the time a preceding article is caused to change the direction of its movement because such contact would be practically certain to result in substantial damage to both articles, in clogging of the receiving station and in substantial losses in output. Attempts to uniformize the speed of successive articles in the conveyor pipe by braking devices have failed to remedy the situation because, if the braking force is sufficiently high to ensure adequate deceleration of rapidly advancing articles, the braking member or members are likely to damage or destroy such articles. On the other hand, if the braking action is less pronounced, the articles are likely to advance past and beyond the braking member or members without adequate deceleration so that such articles strike against the trailing ends of the preceding articles and interfere with proper singularization as well as with proper changes in the direction of movement of successive articles at the receiving station. It has been found that many articles advance past and beyond the braking member or members practically without any deceleration. Such unbraked or insufficiently braked articles rapidly catch up with the preceding articles and invariably interfere with the singularization of articles ahead of as well as with deflection of articles at the receiving station. Excessive braking is equally undesirable because the wrappers of the articles are likely to undergo permanent deformation or to be destroyed on contact with the braking member or members.
Additional problems arise when the transporting system employs a relatively long pneumatic conveyor pipe which includes straight as well as arcuate portions. The articles in such conveyor pipes are likely to pile up into one or more long or very long series of abutting articles (the so-called D-trains) which advance at a relatively low speed and must be broken up ahead of the receiving station in order to prevent the development of bottlenecks.